Rate-dependent hydroelastic response of self-adaptive composite propellers in fully wetted and cavitating flows

Abstract

The objectives of this work are to investigate the fully wetted and cavitating performance of a self-adaptive composite propeller and its dependence on the propeller rotational frequency (RPM or revolution per minute) in addition to the advance coefficient and ambient pressure. Self-adaptive composite propellers are designed to take advantage of the intrinsic deformation coupling behavior of anisotropic composites to improve propeller performance via automatic, passive blade pitch adjustment in spatially or temporally varying flow. The design methodology, numerical and experimental studies of selfadaptive composite propellers in fully wetted flow can be found in [1-7]. In past studies, the primary focus was the fully wetted performance of the composite propellers operating at the design RPM. However, since the deformations of adaptive composite propellers depend on the hydrodynamic load, which in turn depends on the propeller RPM, the response of adaptive composite propellers depend on both the advance coefficient and RPM. Moreover, at high RPMs, composite propellers may be subject to resonant vibration failure due to the inherent flexibility needed to achieve the desired self-adaptive behavior, and due to the decrease in natural frequency caused by added mass effects. Hence, it is important to evaluate the ratedependent behavior of self-adaptive composite propellers. It is also important to evaluate the cavitating performance of self-adaptive composite propellers since cavitation can lead to thrust breakdown, decrease in efficiency, as well as erosion and localized impact damage to the composite blades. In this work, a previously validated coupled boundary element method finite element method (BEMFEM) is used to analyze the rate-dependent response of self-adaptive composite propellers in fully wetted and cavitating flows. Implications of the rate-dependent behavior on the design and interpretation of experimental studies, particularly cavitation tunnel studies, are discussed.